A CCFL is a kind of gas-discharge light source, which is widely used as light source for light source device such as backlight module used in thin film transistor liquid crystal display (TFT-LCD), LCD-TV, notebook, or portable digital video disc (DVD).
Referring to FIG. 3, generally a CCFL 10 includes a transparent tube 12, a cold cathode 14, an anode 16, and a fluorescent layer 18. The fluorescent layer 18 is formed on an inner surface of the transparent tube 12. The cold cathode 14 and the anode 16 are respectively disposed at two ends of the transparent tube 12 and are electrically connected to an exterior power source. The transparent tube 12 is filled with mercury vapor and an inert gas.
When the power source supplies a current to the cold cathode and the anode, an electric field therebetween is produced and electrons are emitted from the cold cathode. The electrons are accelerated by the electric field and then collide with gaseous molecules of the mercury vapor and the inert gas. This causes excitation of the mercury vapor and radiation of ultraviolet rays. The ultraviolet rays irradiate a fluorescent material of the fluorescent layer, whereby a part of the ultraviolet rays are converted into visible lights.
The CCFLs are more efficiently than light emitting diodes (LEDs) when they are used in the backlight modules. However, the brightness and the efficiency of CCFLs are not high enough.
What is needed, therefore, is a cold cathode fluorescent lamp with high efficiency and high brightness.